During the processing of animal carcasses in a commercial slaughter facility, certain bacterial contaminants are introduced or are otherwise associated with the carcasses that subsequently impact the safety and storage life of meat products. During the dressing and fabrication of animal carcasses, bacteria are transferred by the hands of workers and by processing equipment from the animal skin to the carcass. Opportunistic pathogenic and spoilage bacteria, which survive the processing, thrive and multiply in the post-processing environment, thus causing health concerns and reducing the storage life of the end products. There are health and commercial benefits which result from decreased populations of pathogenic and spoilage bacteria on meat including increased safety; increased storage life; improved resistance to the subsequent effects of variable storage and shipping conditions; and compliance with strict foreign importing requirements.
The transfer of bacteria from the skins of animals to meat is a major hygienic problem in processing all animal carcasses including poultry, hogs, sheep and cattle. This problem has been dealt with for many decades in commercial slaughter facilities. The initial approaches to reducing bacteria on the surface of the carcass centered on improving handling and dressing procedures on the slaughter floor and overall sanitation procedures in the entire facility. These efforts have been only partially effective. Since bacterial contamination cannot be wholly avoided, improved equipment and techniques for removing or destroying the bacteria on skinned and eviscerated carcasses are needed.
Several process technologies have been developed and applied in the recent past to reduce bacteria on the surface of the carcass in meat and poultry slaughter operations. The most common antimicrobial treatments currently in use on the slaughter floor include varying stages of water wash, acid wash and steam or hot water pasteurization.
In general, destruction or inactivation of bacteria may be accomplished by the process of pasteurization. Pasteurization, as the term is applied in the food industry, is a process by which a very high percentage of food borne population of microorganisms is killed or rendered incapable of reproduction by raising the internal temperature of the microorganisms to a lethal or critically damaging level in a controlled way (usually by holding the temperature of the microorganisms at a fixed temperature for a fixed time). In contrast to food sterilization processes, more care is given in pasteurization to the inherent sensitivity of the food product to heat exposure to provide an optimum balance between the level of microbial destruction and thermal alteration of the food product. A low-temperature, long-time pasteurization process can achieve the same level of microbial destruction as a high-temperature, short-time process, but the effect on the food product will be vastly different. Negative alteration of the carcass meat (cooking) is minimized by selecting short exposure times at higher temperatures.
The prior art discloses several systems for washing, scalding or decontaminating carcasses prior to refrigeration. Proposals for decontamination include spraying dressed carcasses with solutions of chlorine or organic acids; heating carcass surfaces to pasteurizing temperatures with infrared heaters; and water sprays or sheets of water. Simple cleaning of carcasses with water using an oscillating system of sprayers is proposed by Anderson in U.S. Pat. No. 4,377,549. A hot spray scalding apparatus for fowl carcasses is proposed by Harben in U.S. Pat. No. 4,868,950. Most of the prior art proposals process animal carcasses that are moving on the overhead dressing rail.
In U.S. Pat. No. 4,965,911 to Davey and in U.S. Pat. No. 3,523,326 to Ambill, systems are disclosed in which heated water is directed onto carcasses. These references use differing approaches for delivering heated water to the upper, lateral and convoluted areas of carcasses. These areas are often time shielded from the direct line-of-sight trajectory of the water issuing from the distributing means.
The Davey apparatus is designed for treating dressed beef sides. A plurality of longitudinally aligned vertical sheets of heated water (83.5.degree. C.) are introduced from an overflow weir-type distributing means above the carcass. In order to adapt to convoluted surfaces on the lateral surfaces of a carcass, Davey requires a plurality of baffles positioned at various elevations on either side of the carcass. The baffles impinge the vertically descending sheets of water and deflect them laterally to somewhat better contact the carcass's lateral surfaces. Changes in the size and geometry of the carcass requires manual repositioning of the baffles. Furthermore, the use of deflecting baffles has the tendency of breaking up the descending sheets of water and rapidly cooling the water before contacting the surface of the carcass.
In Ambill's apparatus, carcasses are scaled prior to dehairing, using heated water (about 60.degree. C.) introduced from distributing means located on either side of the carcass. The water is deflected laterally under very low pressure to contact the lateral areas of the carcass. The point of discharge of the distributing means is close to the carcass and vertically movable to oscillate between upper and lower positions, thereby accessing the vertical extent of the carcass. A mechanically complex framework is required to enable the vertical movement of the Ambill's water distributing means. Also, the oscillating, vertical movement of the water distributing means provides only intermittent wetting of portions of the carcass surface. The oscillating vertical movement also contributes to the spray-like pattern of the water trajectory.
The foregoing prior art techniques for reducing the bacteria counts on the surface of the carcass during the slaughter operation suffer various drawbacks. Some techniques have not proven effective in the long term elimination of bacteria on the carcass. This is, quite naturally, the major problem that the commercial slaughter industry faces.
Steam and hot water pasteurization, although both are partially effective in eliminating bacteria, add significant expense to the operation. Steam pasteurization has high equipment and operating costs. Hot water pasteurization, while having reduced equipment costs compared to steam, has very high operating costs as a result of the large volume of water necessary in practicing this technique.